Holding-down means for fixing battery cells in a battery submodule, and battery submodule

ABSTRACT

The invention relates to a holding-down means ( 100 ) for fixing battery cells ( 2 ) in a battery submodule ( 70 ), comprising positioning elements for positioning the holding-down means ( 100 ) relative to the battery cells ( 2 ), and comprising guide elements for guiding cell connectors ( 80 ) which connect the battery cells ( 2 ), wherein gas-venting openings which pass through from a top side to a bottom side are provided in a central region of the holding-down means ( 100 ), and wherein the sealing elements which surround the gas-venting openings are provided on the bottom side of the holding-down means ( 100 ). The invention also relates to a battery submodule ( 70 ) which comprises a plurality of battery cells ( 2 ) and cell connectors ( 80 ) which connect the battery cells ( 2 ), and also at least one holding-down means ( 100 ) for fixing the battery cells ( 2 ).

BACKGROUND OF THE INVENTION

The invention relates to as holding-down means for fixing battery cellsin a battery submodule and to a battery submodule which comprises aholding-down means according to the invention.

Electric energy can be stored by means of batteries. Batteries convertchemical reaction energy into electric energy. In so doing, primarybatteries and secondary batteries are differentiated. Primary batteriesare only functional once, whereas secondary batteries, which are alsoreferred to as accumulators, can be recharged. A battery comprises inthis case one or a plurality of battery cells.

So-called lithium-ion battery cells are particularly used in anaccumulator. These are characterized among other things by high energydensities, thermal stability and an extremely low self-discharge.Lithium-ion batteries are used inter alia in motor vehicles,particularly in electric vehicles (EV), hybrid vehicles (hybrid electricvehicle, HEV) as well as in plug-in hybrid vehicles (plug-in hybridelectric vehicle, PHEV).

A generic battery cell is, for example, disclosed in the German patentapplication DE 10 2012 217 451 A1. The battery cell has a cell housingwhich is, for example, made from metal. The cell housing is designedprismatically, in particular cuboid-shaped, and formed in apressure-resistant manner. The battery thus has a positive terminal anda negative terminal for electrical contacting.

A plurality of battery cells are consolidated to form a batterysubmodule and connected electrically to one another. To this end, thebattery cells are arranged in a common housing or box, and the terminalsof the battery cells are connected to one another by means of cellconnectors. A plurality of battery submodules form a battery.

Holding-down means, which fix the battery cells in the submodule intheir position, are known in order to prevent battery cells from movingrelative to one another as a result of impacts, for example duringtransport. Such a movement could lead to the cell connectors tearingoff.

A battery module having a plurality of battery cells is known from theAmerican patent application US 2012/0244397 A1. The battery modulecomprises a latticed frame for receiving the battery cells and retainingstraps for fixing the battery cells in the frame.

Furthermore, a battery module is known from the American patentapplication US 2012/0177970 A1, which has a plurality of battery cellsthat are arranged and fixed in a latticed frame.

A battery module having a plurality of battery cells, which areconnected to one another by means of cell connectors, is likewise knownfrom the American patent application US 2014/0255750 A1.

A battery cell with a metallic housing is disclosed in the Americanpatent application US 2014/0349152 A1. The terminals of the battery cellare thereby insulated from the metallic housing by means of insulators.

SUMMARY OF THE INVENTION

A holding-down means for fixing battery cells in a battery submodule isproposed, which comprises positioning elements for positioning theholding-down means relative to the battery cells and guide elements forguiding cell connectors which connect the battery cells. As a result,individual battery cells are prevented from moving vertically relativeto one another and cell connectors are prevented from tearing off.

According to the invention, gas-venting openings which pass through froma top side to a bottom side are provided in a central region of theholding-down means, wherein sealing elements which surround thegas-venting openings are provided on the bottom side of the holding-downmeans. When bearing against a battery cell, such a sealing elementserves to laterally seal the gas-venting opening.

According to an advantageous modification to the invention, tolerancecompensation elements are provided on the top side of the holding-downmeans. The tolerance compensation elements ensure a tolerancecompensation between the battery cells and a further battery submodulearranged above said battery cells.

According to a further advantageous modification to the invention, cableguides for guiding electric cables are provided.

The guide elements are preferably designed as guide openings which passthrough from the top side to the bottom side. The guide openings areused here to receive the cell connectors.

The guide elements advantageously comprise at least one first step tosupport the cell connector and a second step. Creepage distances betweenadjacent cell connectors are enlarged by means of the second step.

A battery submodule is also proposed which comprises a plurality ofbattery cells and cell connectors which connect the battery cells aswell as at least one holding-down means according to the invention forfixing the battery cells.

The sealing elements of the holding-down means rest preferably on thebattery cells.

The battery cells advantageously have bursting openings which aresurrounded by the sealing elements of the holding-down means.

The cell connectors preferably engage in guide elements of theholding-down means.

A battery submodule according to the invention is advantageously used inan electric vehicle (EV), in a hybrid vehicle (HEV), in a plug-in hybridvehicle (PHEV), in a stationary battery or in a battery in a marineapplication.

The holding-down means according to the invention allows for a castingof the battery cells within a submodule box of the battery submodule,without the bursting openings of the battery cells being wetted withcasting compound. Hence, a discharge of gases escaping the battery cellsthrough the gas-venting openings is possible throughout the process.

Creepage distances between adjacent cell connectors are enlarged byintroducing the second step into the guide openings of the holding-downmeans. As a result, the danger of short circuits is reduced, inparticular when condensation forms or water accumulates between theterminals.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are explained in greater detail using thedrawings and the following description.

In the drawings:

FIG. 1: shows an exploded view of a battery;

FIG. 2: shows an exploded view of a battery submodule;

FIG. 3: shows a perspective depiction of a holding-down means from thebottom side thereof:

FIG. 4: shows a perspective depiction of the holding-down means fromFIG. 3 from the top side thereof;

FIG. 5: shows a perspective depiction of a battery submodule;

FIG. 6: shows an enlarged depiction of a portion of the batterysubmodule from FIG. 5;

FIG. 7: shows an enlarged depiction of a portion of a holding-down meansaccording to a modification and

FIG. 8: shows an enlarged depiction of a portion of the holding-downmeans according to the modification from FIG. 7 with cell connectors.

DETAILED DESCRIPTION

A battery cell 2 depicted in FIG. 1 comprises a cell housing 11, whichis designed prismatically, in the present example cubically. The cellhousing 11 is designed electrically conductive in the present exampleand is, for example, made from aluminum. The cell housing 11 comprises acuboid container 13, which has a container opening 14 on one side. Thecontainer opening 14 is closed off by means of a cover assembly whichcomprises inter alia a cover plate 23. The cuboid container 13 and thecover plate 23 of the cell housing are in each case designedelectrically conductive and are, for example made from aluminum.

The battery cell 2 comprises a negative terminal 21 and a positiveterminal 22. A voltage provided by the battery cell can be tapped viathe terminals 21, 22. Furthermore, the battery cell 2 can also becharged via the terminals 21, 22. The terminals 21, 22 are disposed soas to be spaced apart from one another on the cover plate 23 of theprismatic cell housing 11.

An electrode winding 3 is arranged within the cell housing 11 of thebattery cell 2, which has two electrodes, namely an anode 5 and acathode, which is not visible in this depiction. The anode 5 and thecathode are in each case designed foil-like and wound with theinterposition of a separator, which is not visible in this depiction, toform the electrode winding 3. The separator is designed in anelectrically insulating manner, but is ionically conductive, i.e. isconducting for lithium ions.

The anode 5 comprises an anodic active material, which is embodied in afoil-like manner. The anodic active material has silicon or an alloycontaining silicon as base material. The anode 5 further comprises acurrent conductor 4 which is likewise embodied in a foil-like manner.The anodic active material and the current conductor 4 of the anode 5are laid flat on one another and are connected to each other. Thecurrent conductor 4 of the anode 5 is designed to be electricallyconductive and is made from a metal, for example from copper. Thecurrent conductor 4 of the anode 5 projects on a first narrow side overan edge of the electrode winding 3 and is connected to a first collector7. The current conductor 4 of the anode 5 is connected electrically tothe negative terminal 21 of the battery cell 2 via the first collector7.

The cathode comprises a cathodic active material which is embodied in afoil-like manner. The cathodic active material has a metal oxide as basematerial, for example lithium cobalt oxide (LiCoO₂). The cathode furthercomprises a current conductor, which is likewise embodied in a foil-likemanner. The cathodic active material and the current conductor are laidflat against one another and are connected to each other. The currentconductor of the cathode is constructed to be electrically conductiveand is made from a metal, for example from aluminum. The currentconductor of the cathode projects on a second narrow side, which liesopposite the first narrow side, over an edge of the electrode winding 3and is connected to a second collector 9. The current conductor of thecathode is electrically connected to the positive terminal 22 of thebattery cell 2 via the second collector 9.

The first collector 7, which is located within the cell housing 11, isconnected to the negative terminal 21, which is located outside of thecell housing 11, by means of as first contact arrangement 18. The secondcollector 9, which is located within the cell housing 11, is connectedto the positive terminal 22, which is located outside of the cellhousing 11, by means of a second contact arrangement 19.

The cell housing 11 of the battery cell 2 is filled with a liquidelectrolyte. The electrolyte surrounds the anode 5, the cathode and theseparator. The electrolyte is also ionically conductive. The electrolyteis filled into the cell housing 11 through a filling opening 26 in thecover plate 23 after the assembly of the cell housing 11. After that,the filling opening 26 is closed by means of a sealing plug that is notdepicted.

The first collector 7 is connected to a first connection bolt 61, whichprojects away from the collector 7 on a side facing away from theelectrode winding 3. The first connection bolt 31 passes through a firstcover opening 24 in the cover plate 23 of the cover assembly 15 and isconnected to the negative terminal 21 at the end thereof facing awayfrom the first collector 7.

The second collector 9 is connected to a second connection bolt 62,which projects away from the second collector 9 on a side facing awayfrom the electrode winding 3. The second connection bolt 62 passesthrough a second cover opening 25 in the cover plate 23 of the coverassembly 15 and is connected to the positive terminal 22 at the endthereof facing away from the second collector 9.

In the present exemplary embodiment, the cover assembly 15 comprises apotential plate 17, which is embodied so as to be electricallyconductive, and which is disposed between the cover plate 23 and thenegative terminal 21. The potential plate 17 connects the cover plate 23electrically to the negative terminal 21. Thus, the cell housing 11 liesat the same electric potential as the negative terminal 21.

The cover assembly 15 further comprises a connection plate 32, which islikewise embodied to be electrically conductive, and which is disposedbetween the cover plate 23 and the positive terminal 22. The connectionplate 32 is connected electrically to the positive terminal 22. Aconnection plate insulation 35 is furthermore mounted, in the presentexample adhesively attached, on the side of the connection plate 32facing away from the cover plate 23, laterally next to the positiveterminal 22.

A spacing insulator 40, which insulates the cover plate 23 electricallyfrom the connection plate 32 and the positive terminal 22, is providedbetween the cover plate 23 and the connection plate 32. The spacinginsulator 40 has an access opening 44, through which the secondconnection bolt 62 projects.

The cover assembly 15 also comprises a cover plate insulation film 36,which is adhesively bonded to the side of the cover plate 23 which facesaway from the container 13. The cover plate insulation film 36 has afirst film opening 37, through which the negative terminal 21 and thepotential plate 17 pass. The cover plate insulation film 36 also has asecond film opening 38, the function of which will be discussed later.The cover plate insulation film 36 also has a third film opening 39through which the positive terminal 22, the connection plate 32, theconnection plate insulation 35 and the spacing insulator 40 pass.

A first connection insulator 46 is provided between the cover plate 23and the first collector 7, said insulator insulating the cover plate 23electrically from the first collector 7. The first connection insulator46 has a first insulator opening 56, through which the first connectionbolt 61 extends. A second connection insulator 47 is provided betweenthe cover plate 23 and the second collector 9, which insulates the coverplate 23 electrically from the second collector 9. The second connectioninsulator 47 has a second insulator opening 57, through which the secondconnection bolt 62 extends.

A first sealing ring 51 is disposed between the first connection bolt 61and the cover plate 23. The first sealing ring 51 is thereby placedaround the first connection bolt 61 and is located in the first coveropening 24 of the cover plate 23. The first sealing ring 51 insulatesthe first connection bolt 61 electrically from the cover plate 23. Inaddition, the first sealing ring 51 seals the first cover opening 24 inan air-tight and fluid-tight manner. Thus, particularly a penetration ofmoisture through the first cover opening 24 into the cell housing 11 aswell as an escape of electrolyte through the first cover opening 24 outof the cell housing 11 is prevented.

A second sealing ring 52 is disposed between the second connection bolt62 and the cover plate 23. The second sealing ring 52 is thereby placedaround the second connection bolt 62 and is located in the second coveropening 25 of the cover plate 23. The second sealing ring 52 insulatesthe second connection bolt 62 electrically from the cover plate 23. Inaddition, the second sealing ring 52 seals the second cover opening 25in an air-tight and fluid-tight manner. Thus, particularly a penetrationof moisture through the second cover opening 25 into the cell housing 11as well as an escape of electrolyte through the second cover opening 25out of the cell housing 11 is prevented.

The cover plate 23 of the cell housing 11 further comprises a burstingopening 33, which is closed by a bursting disc 34. In the event ofexcess pressure within the cell housing 11, the bursting disc 34 openswhereby the excess pressure can escape to the outside through thebursting opening 33. As a result, a bursting of the cell housing 11 isprevented. The bursting opening 33 in the cover plate 23 is then flushwith the second film opening 38 in the cover plate insulation film 36.

In the present exemplary embodiment, the battery cell 2 also has an overcharge safety device (OSD). The over charge safety device comprises anOSD opening 29, which is closed by an OSD membrane 28, provided in thecover plate 23 of the cell housing 11. The OSD membrane 28 is embodiedas thin metal foil. In the event of excess pressure within the cellhousing 11, which can occur by means of a temperature increase as aresult of an overcharge of the battery cell, the OSD membrane 28 deformsand thereby touches the connection plate 32. To this end, the spacinginsulator 40 has a short circuit opening 42 through which the OSDmembrane can extend in the case of a deformation. As a result, a shortcircuit develops between the cell housing 11 and the second collector 9,whereby a charging process of the battery cell 2 is interrupted.

In FIG. 2, an exploded view of a battery submodule 70 is shown. Thebattery submodule 70 comprises as plurality, here twelve, battery cells2 which are disposed within a submodule box 72. After the insertion ofthe battery cells 2 into the submodule box 72, said box is filled with acasting compound 78, which subsequently surrounds the battery cells 2.

The terminals 21, 22 of the battery cells 2 are connected electricallyto one another by means of cell connectors 80. Busbars 73, which areconnected to the negative terminal 21 of one battery cell 2 and to thepositive terminal 22 of another battery cell 2, are used in order toelectrically connect the battery submodule 70.

The battery cells 2 are fixed in the submodule box 72 of the batterysubmodule 70 by means of two holding-down means 100. Coverings 71 reston the holding-down means 100. A cable harness 154 is laid between thecoverings 71 and the holding-down means 100. The cable harness 154comprises individual cables 152, which are connected to the cellconnector 80.

In FIG. 3, a perspective depiction of a holding-down means 100 is shownfrom the bottom side 106 thereof. The holding-down means 100 comprisespositioning elements 110 for positioning the holding-down means 100relative to the battery cells 2. The holding-down means 100 furthercomprises guide elements 120 for guiding the cell connectors 80. Theguide elements 120 are designed in this case as guide openings whichpass continuously from the bottom side to an opposing top side.

Gas-venting openings which pass through from the bottom side to the topside are provided in a central region 102. Sealing elements 132 arefitted on the bottom side, which surround the gas-venting openings 130.

In FIG. 4, a perspective depiction of the holding-down means 100 fromFIG. 3 is shown from the top side 104 thereof. Tolerance compensationelements 140 are arranged on the top side 104. The tolerancecompensation elements 140 are designed to be flexible and compressibleand project approximately at right angles from the top side 104 of theholding-down means 100.

An assembled battery submodule 70 is perspectively depicted in FIG. 5.The battery submodule 70 comprises the components already shown anddescribed in FIG. 2, wherein the coverings 71 are not depicted.

The two holding-down means are set on the battery cells 2 in such a waythat the gas-venting openings 130 surround the bursting openings 33. Thesealing elements 132, which are not visible here, rest on the coverplates 23 of the battery cells.

A cable 152 is connected to each cell connector 80. The cables 152 areput together to form the cable harness 154, and the cable harness is ledout of the submodule box 72. Cable guides 150 are fitted to theholding-down means 100, said cable guides being used to guide the cables152 as well as the cable harness 154.

A portion of the battery submodule 70 from FIG. 5 is shown in anenlarged depiction in FIG. 6. The gas-venting openings 130 of theholding-down means 100 shown surround the bursting openings 33 of thebattery cells 2 lying thereunder. The sealing elements 132 rest on thecover plates 23 of the battery cells. When casting the battery cells 2within the submodule box 72 with the casting compound 78, the sealingelements 132 prevent the sealing compound 78 from wetting and closingthe bursting openings 33 of the battery cells.

In FIG. 7, an enlarged depiction of a portion of a holding-down means100 is shown according to a modification. The guide elements 120designed as guide openings thereby comprise in each case a first step121, which is used to support the cell connectors 80. The guide elements120 each further comprise a second step 122, which is disposed betweenthe first step 121 and the top side 104.

In FIG. 8, an enlarged depiction of the portion of the holding-downmeans 100 according to the modification from FIG. 7 is depicted withcell connectors 80. The cell connectors 80 lie in each case on the firststep 121 of the guide elements 120. The first steps 121 are covered bythe cell connectors 80. The cell connectors 80 thus engage in the guideelements 120 of the holding-down means 100.

The invention is not limited to the exemplary embodiments described hereand to the aspects emphasized therein. A multiplicity of modifications,which lie within the scope of the action of the person skilled in theart, is instead possible within the ranges specified by the claims.

What is claimed is:
 1. A holding-down apparatus (100) for fixing batterycells (2) in a battery submodule (70), comprising: positioning elements(110) for positioning the holding-down apparatus (100) relative to thebattery cells (2), guide elements (120) for guiding cell connectors (80)which connect the battery cells (2), gas-venting openings (130) whichpass through from a top side (104) to a bottom side (106) in a centralregion (102) of the holding-down apparatus (100), and sealing elements(132) positioned on the bottom side of the holding-down apparatus, eachsealing element being a ring surrounding a respective gas-ventingopening (130).
 2. The holding-down apparatus (100) according to claim 1,further comprising tolerance compensation elements (140) on the top side(104) of the holding-down apparatus (100).
 3. The holding-down apparatus(100) according to claim 1, further comprising cable guides (150) forguiding electric cables (152).
 4. The holding-down apparatus (100)according to claim 1, characterized in that the guide elements (120) areconfigured as guide openings which pass through from the top side (104)to the bottom side (106).
 5. The holding-down apparatus (100) accordingto claim 1, characterized in that the guide elements (120) comprise afirst step (121) for supporting the cell connectors (80) and a secondstep (122).
 6. A battery submodule (70), comprising a plurality ofbattery cells (2), cell connectors (80) which connect the battery cells(2) and at least one holding-down apparatus (100) for fixing the batterycells (2), the holding-down apparatus comprising: positioning elements(110) for positioning the holding-down apparatus (100) relative to thebattery cells (2), guide elements (120) for guiding cell connectors (80)which connect the battery cells (2), gas-venting openings (130) whichpass through from a top side (104) to a bottom side (106) in a centralregion (102) of the holding-down apparatus (100), and sealing elements(132) positioned on the bottom side of the holding-down apparatus,wherein each sealing element is a ring surrounding a respective gasventing opening and engaging a cover plate of one of the battery cells.7. The battery submodule (70) according to claim 6, characterized inthat the battery cells (2) have bursting openings (33), which aresurrounded by the sealing elements (132) of the holding-down apparatus(100).
 8. The battery submodule (70) according to claim 6, characterizedin that the cell connectors (80) engage in the guide elements (120) ofthe holding-down apparatus (100).
 9. A vehicle comprising a batterysubmodule (70) according to claim 6, wherein the vehicle is an electricvehicle (EV), a hybrid vehicle (HEV), or a plug-in hybrid vehicle(PHEV).
 10. The battery submodule according to claim 6, furthercomprising tolerance compensation elements (140) on the top side (104)of the holding-down apparatus (100).
 11. The battery submodule accordingto claim 6, further comprising cable guides (150) for guiding electriccables (152).
 12. The battery submodule according to claim 6,characterized in that the guide elements (120) are configured as guideopenings which pass through from the top side (104) to the bottom side(106).
 13. The battery submodule according to claim 6, characterized inthat the guide elements (120) comprise a first step (121) for supportingthe cell connectors (80) and a second step (122).
 14. The holding-downapparatus (100) according to claim 1, characterized in that the sealingelements (132) of the holding-down apparatus (100) rest on the batterycells (2).
 15. The holding-down apparatus (100) according to claim 14,characterized in that the battery cells (2) have bursting openings (33),each of which are surrounded by the sealing elements (132) of theholding-down apparatus (100).
 16. The holding-down apparatus (100)according to claim 1, characterized in that the cell connectors (80)engage in the guide elements (120) of the holding-down apparatus (100).